Prior art pedal assemblies generally comprise a pedal housing attached to a vehicle body and a pedal arm pivotally supported by the pedal housing. A series of links and levers, or cables, mechanically connect the pedal assembly to an engine throttle. Therefore, movement of the pedal arm mechanically controls a position of the engine throttle. In addition, a kickdown device is mechanically connected to the pedal assembly. The kickdown device is used to initiate a kickdown, i.e., a downshift to a next lower gear in an automatic transmission. Typically, such downshifts occur when a user desires fast acceleration. For instance, when the pedal arm is pivoted from an idle position to a predetermined operable position, the kickdown device is mechanically engaged to downshift the automatic transmission. As a result, an added force is required to further pivot the pedal arm. This added force provides a sensation to the user that is commonly referred to as a kickdown feel, i.e., the user can “feel” when the kickdown device is engaged, and hence, when the automatic transmission downshifts to the next lower gear.
Consequently, a large amount of packaging space must be provided within the vehicle to accommodate the mechanical connections to the kickdown device and the engine throttle. However, the space available for the mechanical connections is limited. Hence, recent improvements in the prior art use electrical connections in place of the mechanical connections. Instead of using the mechanical connections to mechanically transmit a position of the pedal arm to the engine throttle or kickdown device, an electrical generator is used to electrically transmit the position of the pedal arm and subsequently control the engine throttle and the kickdown. Replacing the mechanical connections with electrical connections reduces the necessary packaging space for the pedal assembly.
In prior art electronic pedal assemblies, the electrical generator generates a control signal that varies in magnitude with respect to the position of the pedal arm relative to the pedal housing. The control signal is sent to a controller that is responsive to the electrical generator. A processor in the controller uses the control signal to generate other control signals to control the position of the engine throttle and to control the downshift. In general, the downshift occurs when the control signal has a predetermined magnitude and the controller, in response, instructs the automatic transmission to downshift to the next lower gear. In other words, the controller is programmed to control the automatic transmission to downshift to the next lower gear when the control signal has the predetermined magnitude.
Unfortunately, without the mechanical connections, electronic pedal assemblies do not provide the customary feel and performance of a mechanically connected pedal assembly. In other words, the pedal assembly does not provide the kickdown feel to the user when the downshift occurs, i.e., the user cannot “feel” when the downshift occurs. To solve this problem, manufacturers incorporate a kickdown mechanism in the electronic pedal assembly to provide the kickdown feel to the user. The kickdown mechanism is markedly different than the kickdown device described above. The kickdown device is mechanically connected to the pedal assembly via a link or cable and mechanically initiates the downshift in the automatic transmission. Conversely, the kickdown mechanism does not initiate the downshift. Unlike the kickdown device, the kickdown mechanism is a stand-alone mechanism simply used to provide the kickdown feel to the user. Typically, the kickdown mechanism provides the added force associated with the kickdown feel via a kickdown member that engages a portion of the pedal arm.
An example of a kickdown device mechanically connected to the pedal assembly to initiate a downshift in an automatic transmission is shown in U.S. Pat. No. 5,697,253 to Papenhagen et al.
An example of a kickdown mechanism used in an electronic pedal assembly to provide a kickdown feel is shown in U.S. Pat. No. 6,418,813 to Lewis. The pedal assembly of the '813 patent comprises a pedal housing and a pedal arm pivotally engaging the pedal housing. A kickdown housing is attached to the pedal housing and defines a kickdown chamber for receiving a kickdown member. The kickdown member defines a recess and is slidable within the kickdown chamber between a rest position and a plurality of active positions. A rod is springably seated within the recess when the kickdown member is in the rest position and moves out of the recess when the kickdown member moves from the rest position to one of the plurality of active positions to provide the kickdown feel. A spring biases the rod into the recess. With only one rod and recess, the forces acting in a vertical plane on the kickdown member are uneven. The kickdown member is biased upwardly within the kickdown housing which may cause uneven wear on the kickdown member.